High-Resolution Measurements of Multi-Isotopic Signatures (δ15N, δ18O, and Δ17O) of Winter NO2 in a Megacity in Central China

作者：Zhongyi Zhang, Tao Zhou, Zhuang Jiang, Tianming Ma, Guangming Su, Xueyin Ruan, Yichao Wu, Yanzhi Cao, Xia Wang, Zeqian Liu, Weikun Li, Haoyu Zhang, Mengwei Lin, Pu‐Kun Liu, Lei Geng · 发表于：Environmental Science & Technology · 年份：2025 · DOI：10.1021/acs.est.4c07724 · 被引用次数：10 · 研究领域：Atmospheric chemistry and aerosols、Isotope Analysis in Ecology、Atmospheric Ozone and Climate

Isotopic compositions (δ 15 N, δ 18 O, and Δ 17 O) of nitrogen dioxide (NO 2 ) are crucial proxies for elucidating the sources and transformations of atmospheric NO 2, yet observations remain scarce. Here, we reported high-resolution (2 h interval) measurements of NO 2 isotopic compositions in a megacity in Central China. Δ 17 O(NO 2 ) exhibited a clear diurnal cycle with elevated values during the day versus night. Daytime Δ 17 O(NO 2 ) varying from 20.2 to 40.1‰ can be explained by variations in ozone (O 3 ) versus peroxyl radical oxidation of nitric oxide (NO). The estimated peroxyl radicals were positively correlated with photochemical oxidants (O x = O 3 + NO 2 ), revealing the ability of Δ 17 O(NO 2 ) to reflect changes in the atmospheric oxidation environment. Nighttime Δ 17 O(NO 2 ) variations (12.9 to 29.8‰) can be categorized into three regimes: the first regime when Δ 17 O(NO 2 ) stabilized at approximately 20‰ can be well explained by Δ 17 O transfer from O 3; the increases of Δ 17 O(NO 2 ) above 20‰ were attributed to the vertical mixing of residual layer air with elevated Δ 17 O(NO 2 ) and the exchange process between NO 2 and dinitrogen pentoxide; and as low as 12.9‰ Δ 17 O(NO 2 ) can be explained by primary NO 2 emissions and the exchange process between NO and NO 2 . The NO–NO 2 exchange also elevated δ 15 N(NO 2 ), consistent with the observed negative relationships between Δ 17 O(NO 2 ) and δ 15 N(NO 2 ) at night.